A few systems of gene transfer into Gluconobacter oxydans were reported in previous publications. Murooka et al. (J. Bacteriol. 145, 358-368 [1981]) reported conjugal mating of a strain of Gluconobacter oxydans with a strain of Escherichia coli harboring RP4::Mu. The frequency of appearance of a transconjugant was 10.sup.-10 /recipient. Fukaya et al. (Agric. Biol. Chem. 49, 2407-2411 [1985]) reported transformation of Gluconobacter oxydans with a recombinant plasmid which was constructed from an endogenous plasmid of Gluconobacter oxydans and a plasmid of Escherichia coli. The transformation frequency was very low (about 10.sup.2 transformants/.mu.g DNA; in other words, about 10.sup.-9 transformants/recipient). Thus, these systems are not satisfactorily efficient for a gene transfer into Gluconobacter oxydans.
Usually, it is required to obtain thousands of transconjugants or transformants in one experiment for a practical use, e.g., for construction of a genomic library.